Ferroelastic domain switching toughening in Ce-Y-La co-stabilized zirconia ceramics obtained from coated starting powders

While ensuring good resistance to hydrothermal or high-temperature aging of zirconia ceramics, constant attempts to understand and improve their fracture toughness remain the focus. In this work, 0.1 -0.3 mol.% of La2O3 was doped into a 1.5 mol.% Y2O3 +5.5 mol.% CeO2 co-stabilized zirconia ceramic (C1.5Y5.5Ce) based on a coating route. Compared with conventional 3 mol.% Y 2 0 3 stabilized zirconia (C3Y), their microstructure, mechanical properties, and corresponding toughening mechanisms were studied by XRD, SEM, Raman spectroscopy, XPS and TEM. Non-transformable t' zirconia phase was found in both Ce-Y and Ce-Y-La co-stabilized ceramics. Tetragonal to monoclinic (t-m) phase transformation toughening combined with ferroelastic domain toughening is considered to be the primary toughening mechanism of these ceramics. Doping of La2O3 causes significant grain refinement, which increases the hardness and facilitates the ferroelastic domain switching. The oxygen vacancy concentration and the valence state of cerium are also affected, resulting in a change in the tetragonal stability. Although with a lower t-m transformation rate, the 0.3 mol.% La2O3 doped C1.5Y5.5Ce possessing the smallest grain size shows a high fracture toughness of 10.17 MPa m(1/2), which is about 23% higher than that of C3Y. (C) 2019 Elsevier B.V. All rights reserved.